<html>
  <head>
    <style>
      body {
        background-color: cadetblue;
      }
    </style>
  </head>
  <body>
    <span>iframe origin:</span>
    <span id="origin"></span>
    <script>
      document.getElementById('origin').textContent = window.origin;
      parent.postMessage({ mph: 99 }, window.origin);
    </script>
  </body>
</html>
